1. Field of the Invention
The present invention relates to a clamping apparatus, and more specifically to a clamping apparatus of the type adapted to rotate one of two threaded members threadably engaged to each other so as to axially advance and retreat the other threaded member for driving a clamping member connected to the other threaded member.
2. Description of Prior Art
As such apparatus there has been known the one, for example as disclosed in the Japanese Utility Model Publication No. 49-36057.
In this apparatus, a bolt is threadably engaged with both a connecting internal thread formed in an object to be clamped and an advancing/retreating internal thread formed in a support base so as to be able to advance and retreat, and the bolt is directly rotated by an electric motor fixed to the support base.
There are, however, following problems associated with the above-mentioned conventional apparatus.
Although the object to be clamped and the support base are connected by the bolt, a screw clearance exists between the connecting internal thread of the object to be clamped and an external thread of the bolt as well as a screw clearance exists also between the advancing/retreating internal thread of the support base and the external thread of the bolt. Therefore, a force pulling the object to be clamped and the support base to each other is hardly produced between them.